This seastar has a small central disk and 5 long rays (total diameter is 5 to 7.6 times central disk diameter) which are not bordered by obvious marginal plates (photo). The rays usually narrow as they attach to the central disk and are widest at a point slightly out from the central disk. Exposed ossicle spines (less than 2 mm high, irregular pattern) and pedicellariae make the aboral surface rough (photo). Clusters of pedicellariae are especially visible near the ambulacral grooves, and are usually in clumps at the bases of spines. Has both crossed and straight pedicellariae. Color highly variable: gray, blue-gray, greenish, brown, orange, reddish (especially along the Oregon and California coast), pale purple; frequently margins of rays are a different shade than aboral surface. Radius up to 28 cm.